Hydrogen-controlled structural reconstruction of palladium-bismuth oxide cluster to single atom alloy for low-temperature CO oxidation

Palladium (Pd) has been widely regarded as a high-performance catalyst for various oxidative reactions, however, the actual structure of active site remains controversial due to structural evolution under operation conditions. Herein, we prepared a series of bismuth (Bi)-doped silica-supported Pd catalysts and found a hydrogen-controlled structural reconstruction mechanism of palladium-bismuth oxide cluster to single atom alloy to efficiently catalyze low-temperature CO oxidation. The formation of PdxBiyOz clusters with unique Pd−O−Bi coordination structure could enhance the sinter-resistance ability of Pd species. This structural evolution of active site is clearly uncovered by in-situ XAFS results, in which metallic Bi−Pd shell gradually generates as the increase of reduction temperature without any metallic Bi−Bi bond. More importantly, PdBi1 single atom alloy exhibits a good CO oxidation activity with a CO2 production rate of 413 μmolCO2·gPd−1·s−1 at 100 °C and excellent catalytic stability. Density function calculation (DFT) results indicate that there are geometric and electronic effects between Bi and Pd atoms, which favor total linear-CO adsorption, activate CO and O2 molecules, and reduce the barrier for the formation of OO-CO intermediates in PdBi1 single atom alloy.